"These conditions of luminosity (luminiferous ether) have no thermal force associated with them; although, paradoxically, all thermal conditions emanate from that source. The tenuity of this element accounts for it. It is only when these sympathetic streams come in conflict with the cruder elementary conditions, either the molecular or atomic, that heat is evolved from its latent state, and a different order of light from the etheric luminous is originated, which has all the high conditions of thermal force associated with it; the sun being the intermediate transmitter. Thus is shown the wonderful velocity of these sympathetic streams emanating from the celestial." [Keely and His Discoveries pg 271]
See Also
Heat
thermal concentration
Isothermal Process
Thermal Runaway